Both way of playing

[Lumaud]

It's possible to start as single player and later go to play on line? 

Or to play both in different times, of course? 

Thks

[Foxtrot]

You can interchange between the two, but they're completely different experiences.  You can't carry anything in-game from online to story mode or the other way around.

So any gold you get from treasure hunts or weapons in story mode won't magincally appear when you enter the Online game.